An Unprecedented Fe^III(μ-OH)Zn^II Complex that Mimics the Structural and Functional Properties of Purple Acid Phosphatases

This communication reports the synthesis and X-ray structure of the first mixed-valence FeIIIZnII complex containing the FeIII(μ-OH)ZnII structural unit. Based on the structure, physicochemical solution studies, and the catalytic properties toward the hydrolysis of the diester 2,4-bis(dinitrophenyl)phosphate (BDNPP), it is proposed that complex 1 employs a hydrolytic mechanism similar to that proposed for red kidney bean purple acid phosphatase, including a nucleophilic attack by the terminal, FeIII-bound hydroxide and the concomitant release of 2,4-dinitrophenolate. Furthermore, it is demonstrated that the μ-hydroxo group in the {FeIII(μ-OH)(μ-ROPO3)ZnII} intermediate is unable to hydrolyze the monoester 2,4-dinitrophenylphosphate (DNPP), which suggests that the μ-hydroxo group is a significantly poorer nucleophile than the terminally FeIII-bound OH- group.